This invention relates to an electrical receptacle, and more particularly to a receptacle generally similar to those used for cigar lighters to receive a plug for connecting a 6-volt or 12-volt power source to a light or electrical appliance.
Known cigar lighter type receptacles currently being manufactured employ a design concept in which a housing and negative contact of one piece is formed into a deep drawn steel cup. The steel cup has lanced fingers running axially to provide friction on the ash guard of the lighter and is provided with means at the bottom of the cup to receive a ceramic insulator. By various means depending upon the specific manufacturer's design, a male screw thread member is fitted to the closed end of the cup to mate with a deep drawn nut member designed to hold the receptacle in the dash board of an automobile and, depending upon its tightness, to create a ground contact. The aforementioned ceramic insulator is centered in the well and is designed to receive a bi-metal assembly which makes the positive contact with the cigar lighter. When the heating element of the cigar lighter is pressed down into the well, positive contact is made with the outside of the heating element of the bi-metals. The heating element conducts heat to the bi-metals which are designed to distort with heat so that they release the lighter assembly and allow it to "pop out". The lighter assembly will pop out to the extent that is allowed to do so by the lanced fingers in the negative contact well which hold the ash guard in position precluding the lighter from popping completely out of the well.
Adapter plugs were subsequently designed so that trouble lights and other electrical appliances having their own cords could be used in or around automobiles, without requiring the user to provide any special receptacle or connecting means. Such adapter plugs typically comprise a body for insertion into a cigar lighter receptacle, with spring loaded members at the end and on one side to make contact respectively with the bi-metal element and the steel cup.
Extension cords could, of course, use the same type of adapter plug at one end, and require a receptacle at the other end. It was natural to use the standard cigar lighter receptacle design to the maximum extent possible. In one design of a receptacle, the bi-metallic element is removed and replaced by a brass machine screw to make the positive contact and the well is modified only by the deletion of the side lances, which are of course not required for cooperating with adapter plugs. This receptacle is now used as a standard structure for extension cord receptacles. With the advent of recreational vehicles and similar requirements for sources of 12-volt electrical power, these receptacles are also mounted into wall plates for use as 12-volt convenience outlets. For extension cord use, a plastic device similar in shape to a standard bicycle handle grip may be placed around the outside of the receptacle to enhance its appearance and to prevent damage to the electrical connections.
Efforts have been made to reduce the cost of extension cord receptacles by modifying the known product, and also by assembly with available parts, but these efforts have been unsuccessful. There are also certain limitations on existing receptacles from the standpoint of current-carrying capability.